黑素瘤细胞对失巢凋亡的抗性需要Mcl-1。

Mcl-1 is required for melanoma cell resistance to anoikis.

作者信息

Boisvert-Adamo Karen, Longmate Whitney, Abel Ethan V, Aplin Andrew E

机构信息

Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

出版信息

Mol Cancer Res. 2009 Apr;7(4):549-56. doi: 10.1158/1541-7786.MCR-08-0358.

Abstract

Melanoma is a particularly aggressive tumor type that exhibits a high level of resistance to apoptosis. The serine/threonine kinase B-RAF is mutated in 50% to 70% of melanomas and protects melanoma cells from anoikis, a form of apoptosis induced by lack of adhesion or adhesion to an inappropriate matrix. Mutant B-RAF down-regulates two BH3-only proapoptotic proteins, Bim(EL) and Bad. BH3-only proteins act, at least in part, by sequestering prosurvival Bcl-2 family proteins and preventing them from inhibiting the mitochondrial apoptotic pathway. Several Bcl-2 proteins are up-regulated in melanoma; however, the mechanisms of up-regulation and their role in melanoma resistance to anoikis remain unclear. Using RNA interference, we show that depletion of Mcl-1 renders mutant B-RAF melanoma cells sensitive to anoikis. By contrast, minor effects were observed following depletion of either Bcl-2 or Bcl-(XL). Mcl-1 expression is enhanced in melanoma cell lines compared with melanocytes and up-regulated by the B-RAF-MEK-extracellular signal-regulated kinase 1/2 pathway through control of Mcl-1 protein turnover. Similar to B-RAF knockdown cells, adhesion to fibronectin protected Mcl-1 knockdown cells from apoptosis. Finally, expression of Bad, which does not sequester Mcl-1, further augmented apoptosis in nonadherent Mcl-1 knockdown cells. Together, these data support the notion that BH3 mimetic compounds that target Mcl-1 may be effective for the treatment of melanoma in combinatorial strategies with agents that disrupt fibronectin-integrin signaling.

摘要

黑色素瘤是一种侵袭性特别强的肿瘤类型,对细胞凋亡表现出高度抗性。丝氨酸/苏氨酸激酶B-RAF在50%至70%的黑色素瘤中发生突变,可保护黑色素瘤细胞免受失巢凋亡(一种因缺乏黏附或黏附于不适当基质而诱导的细胞凋亡形式)。突变型B-RAF下调两种仅含BH3结构域的促凋亡蛋白Bim(EL)和Bad。仅含BH3结构域的蛋白至少部分通过隔离促生存Bcl-2家族蛋白并阻止它们抑制线粒体凋亡途径来发挥作用。几种Bcl-2蛋白在黑色素瘤中上调;然而,上调的机制及其在黑色素瘤对失巢凋亡抗性中的作用仍不清楚。利用RNA干扰,我们发现Mcl-1缺失使突变型B-RAF黑色素瘤细胞对失巢凋亡敏感。相比之下,Bcl-2或Bcl-XL缺失后观察到的影响较小。与黑素细胞相比,黑色素瘤细胞系中Mcl-1的表达增强,并且通过控制Mcl-1蛋白周转,由B-RAF-MEK-细胞外信号调节激酶1/2途径上调。与B-RAF敲低细胞类似,黏附于纤连蛋白可保护Mcl-1敲低细胞免于凋亡。最后,不隔离Mcl-1的Bad的表达进一步增强了非黏附性Mcl-1敲低细胞中的凋亡。总之,这些数据支持这样一种观点,即靶向Mcl-1的BH3模拟化合物在与破坏纤连蛋白-整合素信号传导的药物联合使用的策略中可能对黑色素瘤治疗有效。

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